WTF is wrong with my car?

I am having the strangest problem w/ my M3. I can't figure out what the deal is.

My baseline dyno was done in April of 2009. The car had Remus Race mufflers. Everything else was stock. It made 334 rwhp and 250 rwtq on 91 octane gas. Right at the average for a stock 6MT. This was at SP Engineering.

Around October I re-dynoed at Technik in Long Beach. The car was still the same except I'd switched from stock 18s to 19" Volk G2 rims. My best run on their dynojet was only 317rwhp, and the curve was shot to $#@! past 6000rpm. Right after I was on the dyno I went into limp mode and got a CEL. After waiting a minute and re-starting the car the limp mode was gone. We put a scanner on it right away and there were no active, pending, or stored fault codes. No more limp mode incidents have happened.

I went back to SP Engineering to re-dyno against my baseline of 334. This time I made... 338rwhp and 257rwtq. The curve is strange. From 3000 - 6000 RPM it's gained 10-15rwhp over stock. But as soon as I pass 6000, the curve falls sharply until it's almost exactly lined up with stock. It's like something is holding my car back from making top end power.

I thought about replacing my fuel pumps, but the parts alone cost nearly $1,000. I don't want to start throwing money, replacing random parts hoping to find the right one. I figure it could be the spark plugs, coil packs, fuel filter, fuel pumps... I am really confused and frustrated by this. The car definitely makes more power in the low and mid range, but at the top end something is holding it back.

Although a few things could affect the power up top, there is also a possibility that the original dyno is the one that is not correct. A number of things can change between dyno's though. actual weather conditions. fuel used, oil used, oil level, tires used, tire pressure, etc. Much easier to speculate/diagnose with the graph though

No, it's more than that. The way the curve drops after 6,000 RPM makes it clear that something is amiss. I found a thread elsewhere about faulty fuel pump controllers that affected some early build M3s (pre May 08), and my car was built in April 08. So I'm looking into that. I have a feeling it's something pretty simple, like a sensor, a coil pack, or a relay. But tracking it down is the problem. I am hoping to find an expert mechanic who can pinpoint it. My method is to just replace everything, but that could cost thousands and I might never hit the right part.

Anyway, I'll scan my dyno graphs on Monday when I'm back at work and post them up.

Sell the car and buy another used M3. It could be that the "timing" is not properly set(forgot if it's the cams or crank). Maybe a software issue? How many miles on the car when you first got it? Has it been overreved? I kinda doubt that it's the fuel pump though....

Been hesitant about that because of the mods vs. warranty. Plus the quality of dealer mechanics is pretty much a crapshoot. That being said I got in touch with a master tech who is going to look into it.

Originally Posted by GT3

Sell the car and buy another used M3. It could be that the "timing" is not properly set(forgot if it's the cams or crank). Maybe a software issue? How many miles on the car when you first got it? Has it been overreved? I kinda doubt that it's the fuel pump though....

I would take too big a hit selling, plus if I were to sell I'd probably get something else like a Z06. Doubt it's a software issue but anything is possible. It had 30 miles when I first got it. No over revs. We'll see if the tech finds anything. There is a fuel pump controller that is known to occasionally fail.

Replaced O2 sensors and reflashed DME back to the stock using the latest code. My build date was 4/08 so there were a lot of updates. Lost my Powerchip code during the reflash - to be clear, the PC software is not the issue. I was having the power loss and CEL issue when I was still stock. We'll see if the new DME code and sensors fix the problem.

Replaced O2 sensors and reflashed DME back to the stock using the latest code. My build date was 4/08 so there were a lot of updates. Lost my Powerchip code during the reflash - to be clear, the PC software is not the issue. I was having the power loss and CEL issue when I was still stock. We'll see if the new DME code and sensors fix the problem.

Keep us updated.

Hopefully replacing the 02 sensors will help but you also mentioned you might replace the DME itself?

Hopefully replacing the 02 sensors will help but you also mentioned you might replace the DME itself?

The DME was OK so all that was needed was to bump it up (along with all the other modules) to the latest revs. There were 26 modules flashed. Everything from DME, EDC, and DSC to the stereo.

The stored fault code that kept showing up in ISIS was 2743 - Oxygen sensor heater diagnosis before cat, bank 2. The code persisted after the sensor was replaced, but went away after the DME updates. Hopefully that was the cause.

Also, for some reason, the car had been left in PDI mode. The tech had no idea why that would be or if it hurt performance, usually PDI mode is turned off before the customer takes delivery. The original dealership probably forgot to change the setting all the way back when I bought the car.

Something else interesting - the "State Inspection" category under "Service" in iDrive had gone missing a while back, I didn't even notice it was gone until it re-appeared after the DME updates. Seems like a typical BMW electronics bug.

The DME was OK so all that was needed was to bump it up (along with all the other modules) to the latest revs. There were 26 modules flashed. Everything from DME, EDC, and DSC to the stereo.

The stored fault code that kept showing up in ISIS was 2743 - Oxygen sensor heater diagnosis before cat, bank 2. The code persisted after the sensor was replaced, but went away after the DME updates. Hopefully that was the cause.

Also, for some reason, the car had been left in PDI mode. The tech had no idea why that would be or if it hurt performance, usually PDI mode is turned off before the customer takes delivery. The original dealership probably forgot to change the setting all the way back when I bought the car.

Something else interesting - the "State Inspection" category under "Service" in iDrive had gone missing a while back, I didn't even notice it was gone until it re-appeared after the DME updates. Seems like a typical BMW electronics bug.

So does the car feel any different or better? Are you going to flash it again?

Saw some posts on the other forum about detonation and bad bearings, but I don't hear anything that sounds like valves clattering and oil consumption is normal. I still might pull the spark plugs sometime just to take a look at them, see if there's any oil on them and what the gaps are like.